Cake Stencils ?????

I have seen some amazing looking cakes that have stenciling done on them. The cakes I have seen have been iced in Buttercream. I have done a Google search on stencils and found 2 main types of stencils. One is round and the other is rectangle. Am I correct in thinking that the rectangles are used on the sides of the cakes and the rounds are used on the top????

Does anyone have any tips for me before using stencils on BC iced cakes?

Here are some video's on how to stencil. One is for fondant and one is for buttercream. I know you said you wanted it for buttercream but I thought I'd send the fondant one too...just in case you need it some time. Hope this helps.